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.\" Copyright (c) 2009 Oracle and/or its affiliates. All rights reserved.
.\" Copyright (c) 2009 Michael Gebetsroither <michael.geb@gmx.at>. All rights
.\" reserved.
.\" Copyright (c) 2017, Intel Corporation.
.\"
.Dd July 12, 2025
.Dt ZTEST 1
.Os
.
.Sh NAME
.Nm ztest
.Nd was written by the ZFS Developers as a ZFS unit test
.Sh SYNOPSIS
.Nm
.Op Fl VEG
.Op Fl v Ar vdevs
.Op Fl s Ar size_of_each_vdev
.Op Fl a Ar alignment_shift
.Op Fl m Ar mirror_copies
.Op Fl r Ar raidz_disks/draid_disks
.Op Fl R Ar raid_parity
.Op Fl K Ar raid_kind
.Op Fl D Ar draid_data
.Op Fl S Ar draid_spares
.Op Fl C Ar vdev_class_state
.Op Fl d Ar datasets
.Op Fl t Ar threads
.Op Fl g Ar gang_block_threshold
.Op Fl i Ar initialize_pool_i_times
.Op Fl k Ar kill_percentage
.Op Fl p Ar pool_name
.Op Fl T Ar time
.Op Fl z Ar zil_failure_rate
.
.Nm
.Fl X
.Op Fl VG
.Op Fl s Ar size_of_each_vdev
.Op Fl a Ar alignment_shift
.Op Fl r Ar raidz_disks
.Op Fl R Ar raid_parity
.Op Fl d Ar datasets
.Op Fl t Ar threads
.
.Sh DESCRIPTION
.Nm
was written by the ZFS Developers as a ZFS unit test.
The tool was developed in tandem with the ZFS functionality and was
executed nightly as one of the many regression test against the daily build.
As features were added to ZFS, unit tests were also added to
.Nm .
In addition, a separate test development team wrote and
executed more functional and stress tests.
.
.Pp
By default
.Nm
runs for ten minutes and uses block files
(stored in
.Pa /tmp )
to create pools rather than using physical disks.
Block files afford
.Nm
its flexibility to play around with
zpool components without requiring large hardware configurations.
However, storing the block files in
.Pa /tmp
may not work for you if you
have a small tmp directory.
.
.Pp
By default is non-verbose.
This is why entering the command above will result in
.Nm
quietly executing for 5 minutes.
The
.Fl V
option can be used to increase the verbosity of the tool.
Adding multiple
.Fl V
options is allowed and the more you add the more chatty
.Nm
becomes.
.
.Pp
After the
.Nm
run completes, you should notice many
.Pa ztest.*
files lying around.
Once the run completes you can safely remove these files.
Note that you shouldn't remove these files during a run.
You can re-use these files in your next
.Nm
run by using the
.Fl E
option.
.
.Sh OPTIONS
.Bl -tag -width "-v v"
.It Fl h , \&? , -help
Print a help summary.
.It Fl v , -vdevs Ns = (default: Sy 5 )
Number of vdevs.
.It Fl s , -vdev-size Ns = (default: Sy 64M )
Size of each vdev.
.It Fl a , -alignment-shift Ns = (default: Sy 9 ) No (use Sy 0 No for random )
Alignment shift used in test.
.It Fl m , -mirror-copies Ns = (default: Sy 2 )
Number of mirror copies.
.It Fl r , -raid-disks Ns = (default: Sy 4 No for raidz/ Ns Sy 16 No for draid )
Number of raidz/draid disks.
.It Fl R , -raid-parity Ns = (default: Sy 1 )
Raid parity (raidz & draid).
.It Xo
.Fl K , -raid-kind Ns = Ns
.Sy raidz Ns | Ns Sy eraidz Ns | Ns Sy draid Ns | Ns Sy random
(default:
.Sy random Ns
)
.Xc
The kind of RAID config to use.
With
.Sy random
the kind alternates between raidz, eraidz (expandable raidz) and draid.
.It Fl D , -draid-data Ns = (default: Sy 4 )
Number of data disks in a dRAID redundancy group.
.It Fl S , -draid-spares Ns = (default: Sy 1 )
Number of dRAID distributed spare disks.
.It Fl d , -datasets Ns = (default: Sy 7 )
Number of datasets.
.It Fl t , -threads Ns = (default: Sy 23 )
Number of threads.
.It Fl g , -gang-block-threshold Ns = (default: Sy 32K )
Gang block threshold.
.It Fl i , -init-count Ns = (default: Sy 1 )
Number of pool initializations.
.It Fl k , -kill-percentage Ns = (default: Sy 70% )
Kill percentage.
.It Fl p , -pool-name Ns = (default: Sy ztest )
Pool name.
.It Fl f , -vdev-file-directory Ns = (default: Pa /tmp )
File directory for vdev files.
.It Fl M , -multi-host
Multi-host; simulate pool imported on remote host.
.It Fl E , -use-existing-pool
Use existing pool (use existing pool instead of creating new one).
.It Fl T , -run-time Ns = (default: Sy 300 Ns s)
Total test run time.
.It Fl P , -pass-time Ns = (default: Sy 60 Ns s)
Time per pass.
.It Fl F , -freeze-loops Ns = (default: Sy 50 )
Max loops in
.Fn spa_freeze .
.It Fl B , -alt-ztest Ns =
Path to alternate ("older")
.Nm ztest
to drive, which will be used to initialize the pool, and, a stochastic half the
time, to run the tests.
The parallel
.Pa lib
directory is prepended to
.Ev LD_LIBRARY_PATH ;
i.e. given
.Fl B Pa ./chroots/lenny/usr/bin/ Ns Nm ,
.Pa ./chroots/lenny/usr/lib
will be loaded.
.It Fl C , -vdev-class-state Ns = Ns Sy on Ns | Ns Sy off Ns | Ns Sy random No (default : Sy random  )
The vdev allocation class state.
.It Fl o , -option Ns = Ns Ar var Ns = Ns Ar value Ns …
Set the given tunable to the provided value.
.It Fl G , -dump-debug
Dump zfs_dbgmsg buffer before exiting due to an error.
.It Fl V , -verbose
Verbose (use multiple times for ever more verbosity).
.It Fl X , -raidz-expansion
Perform a dedicated raidz expansion test.
.El
.
.Sh EXAMPLES
To override
.Pa /tmp
as your location for block files, you can use the
.Fl f
option:
.Dl # ztest -f /
.Pp
To get an idea of what
.Nm
is actually testing try this:
.Dl # ztest -f / -VVV
.Pp
Maybe you'd like to run
.Nm ztest
for longer? To do so simply use the
.Fl T
option and specify the runlength in seconds like so:
.Dl # ztest -f / -V -T 120
.
.Sh ENVIRONMENT VARIABLES
.Bl -tag -width "ZF"
.It Ev ZFS_HOSTID Ns = Ns Em id
Use
.Em id
instead of the SPL hostid to identify this host.
Intended for use with
.Nm , but this environment variable will affect any utility which uses
libzpool, including
.Xr zpool 8 .
Since the kernel is unaware of this setting,
results with utilities other than ztest are undefined.
.It Ev ZFS_STACK_SIZE Ns = Ns Em stacksize
Limit the default stack size to
.Em stacksize
bytes for the purpose of
detecting and debugging kernel stack overflows.
This value defaults to
.Em 32K
which is double the default
.Em 16K
Linux kernel stack size.
.Pp
In practice, setting the stack size slightly higher is needed because
differences in stack usage between kernel and user space can lead to spurious
stack overflows (especially when debugging is enabled).
The specified value
will be rounded up to a floor of PTHREAD_STACK_MIN which is the minimum stack
required for a NULL procedure in user space.
.Pp
By default the stack size is limited to
.Em 256K .
.El
.
.Sh SEE ALSO
.Xr zdb 1 ,
.Xr zfs 1 ,
.Xr zpool 1 ,
.Xr spl 4
